Carcinogenicity chemical, effect

Some chemicals are believed to have no threshold above which toxic effects are observed. In other words, a single molecule has the potential to induce an adverse effect. The most common group of hazards in this respect are genotoxic carcinogens. Chemical carcinogens are not normally approved as food additives because an acceptable daily intake cannot be established. 

Ideally, a full data set should be available for the hazard assessment of a chemical substance, including animal tests to evaluate the toxicokinetics and the following toxicological properties acute toxicity, irritation, sensitization, toxicity following repeated exposure to the substance, mutagenicity and genotoxicify, carcinogenicity, and effects on fertility and fetal development. 

It is not known how chemicals cause cancer. A fascinating aspect of the story is that many "carcinogenic" chemicals are in fact, not the culprits responsible for cancer induction. The metabolic processes of the body change the chemicals from relatively innocuous substances into reactive intermediates which in as yet unknown fashion, trigger the chain of events which finally result in tumor formation. In other words, chemical carcinogenesis is an effect of "failed" detoxification. 

Risk Index for Mixtures of Hazardous Substances. For the purpose of developing a comprehensive and risk-based hazardous waste classification system, a simple method of calculating the risk posed by mixtures of radionuclides and hazardous chemicals is needed. The method should account for the linear, nonthreshold dose-response relationships for radionuclides and chemical carcinogens (stochastic effects) and the threshold dose-response relationships for noncarcinogenic hazardous chemicals (deterministic effects). 

Kitchin KT (1999) Carcinogenicity Testing, Predicting, and Interpreting Chemical Effects. New York Dekker. 

It is very well known that the phenothiazines alone possess no antitumour and/or antineoplasma activity. But when they are applied in combination with other drugs, the phenothiazines can increase the anticancer activity and provoke a decrease of mutagenesis, diminishing the cytotoxic effects caused by radiation, carcinogenic chemicals and multidrug resistance (MDR). The positive effects of a simultaneous chemotherapy of cancers by combining... 

For all these cancers, incidence rates are highest in the industrially developed areas of the world, where people are exposed to higher levels of carcinogenic chemicals. In each case, those living in areas with lower incidences for a particular cancer demonstrate increased rates when they migrate to areas with higher incidences, further demonstrating the cancer causative effects of environmental and occupational exposures to toxic chemicals. 

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